Method for reducing the occurrence of bowing in wooden window rails

ABSTRACT

Apparatus and a method for reducing the bowing of window rail members constructed from wood by machining a curvature in the member which counteracts the naturally occurring bow. A number of rail members (e.g., a plurality of check rails) are initially stored in a hopper in a horizontally extending, vertically overlaying position. The bottom rail in the hopper is continuously discharged by a drive chain which conveys the rail to a camdriven cutting tool for cutting a concave bow in the rail opposite the side receiving the window pane. Curvature sensing means are associated with the hopper to determine the natural curvature, if any, of each rail, thus, allowing the curvature of the rails to be aligned and the removal of any rail having too large a natural bow to be counteracted by the machined curvature.

United States Paten Peterson. 7 [4 1 Mar. 18, 1975 [54] METHOD FOR REDUCING THE 2,691,394 10/1954 Gifford et al. 144/143 x OCCURRENCE OF ROWING IN WOODEN 2,782,817 2/1957 Steiner 144/117 B 2,830,629 4/1958 Deiters 144/117 B WINDOW RAILS Kenneth L. Peterson, Bayport, Minn.

Assignee: Andersen Corporation, Bayport,

Minn.

Filed: Mar. 12, 1974 Appl. No.: 450,366

Related U.S. Application Data Division of Ser. No. 301,130, Oct. 26, 1972, Pat. No. 3,825,046.

Inventor:

References Cited UNITED STATES PATENTS 5/1959 Tice 144/143 5/1934 Tate 144/143 X Primary Examiner-Andrew R. Juhasz Assistant E.\'ami11er-W. D. Bray [57] ABSTRACT Apparatus and a method for reducing the bowing of window rail members constructed from wood by machining a curvature in the member which counteracts the naturally occurring bow. A number of rail members e.g., a plurality of check rails) are initially stored in a hopper in a horizontally extending, vertically over-laying position. The bottom rail in the hopper is continuously discharged by a drive chain which con-' veys the rail to a cam-driven cutting tool for cutting a concave bow in the rail opposite the side receiving the window pane. Curvature sensing means are associated with the hopper to determine the natural curvature, if any, of each rail, thus, allowing the curvature of the rails to be aligned and the removal of any rail having too large a natural bow to be counteracted by the machined curvature.

2 Claims, 5 Drawing Figures PATENIEU MAR I 8 i975 SHEUIOFS METHOD FOR REDUCING THE OCCURRENCE OF BOWING IN WOODEN WINDOW RAILS This is a divisional application of Ser. No. 301,130, filed onOct. 26, 1972 of Kenneth L. Peterson for Apparatus and Method for Reducing the Occurence of Bowing in Wooden Window Rails now Pat. No. 3,825,046.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention pertains to apparatus and a method for reducing the occurrence of bowing in the rail members of wooden window sashes.

2. Description of the Prior Art Historically, window units in which the sashes are constructed from wood have been widely used. This is true for a variety of reasons, but particularly because of the good insulative characteristics of wood as well as its fine aesthetic appearance. As a result of their wide use, many advances have been made over the years in the art of constructing wooden sashes. However, the problem of reducing the bowing which frequently occurs in wooden rail members (i.e., the head, check and side rails comprising the wooden sash) has 1 long plagued the industry. This bowing occurs primarily for three reasons. First, a sizeable number of the rails have a natural bow. Secondly, the milling of the groove or U-shaped slot in each rail member for receiving and supporting the glass pane results in the removal of more material from the inner face of the rail than the outer surface. As a result, the rail member tends to bow outwardly away from the milled surface. Finally, the utilization of a snap-on bead to seal the glass pane within the wooden sash accentuates any outward bow in the rail member. The problem of bowing is particularly acute for check rails which are typcially the thinnest rail member and thus most prone to bowing.

The problem of bowing is undesirable for a number of reasons. First, the bowed rail members do not fit tightly within the window casing resulting in undesirable heat loss and wind draft. Also, in the case of a lockable double sash window, the lock mechanism frequently does not operate properly since the bowed check rails cause misalignment of the locking members. Finally, the bowed rail members are unsightly, creating the appearance of a low quality window unit. To avoid these disadvantages, two approaches are presently followed. First, rail members with an unacceptably large bow are simply discarded resulting in unnecessary expense and waste of lumber. Also, an attempt is sometimes made to straighten the bowed rails by utilization of various clamping devices to clamp the head and check rails together during the glazing operation. The rails are then retained in this clamped position until the glazing compound has sufficiently hardened to provide adequate adhesion between the glass and rail members to prevent the rails from bowing outwardly when unclamped. This approach is, of course, extremely time consuming and expensive, typically being utilized only when the highest quality window unit is desired.

SUMMARY OF THE INVENTION In its broad form, the present invention Provides a method for substantially reducing the bowing which occurs in wooden rail members such as those used in the 2 construction of window sashes. This is achieved by'cutting a curvature into the wooden rail member along the surface of the opposite the surface milled so as to receive the window pane; this curvature'counteracting the naturally occuring bow and thus providing an end product which is substantially straight. In its preferred form, Applicants invention includes cutting means which includes a blade member for cutting the wooden rails and guide means for urging the rails against the blade. Control means are provided for controlling the relative position of the blade member and the guide means so as to cut a concave curvature into the rail as it passes the blade. Also, a hopper is preferably provided for storing the rail members in a horizontally extending, vertically over-laying relationship. A conveyor is utilized to continuously convey the, bottom one of the stacked rail members past the cutting means.

The present discovery has beenfound to substantially eliminate the bowing in wooden sash members while necessitating very little additional expense in their manufacture. The elimination of such bowing significantly reduces the waste heretofore occurring in the construction of wooden sashes more than offsetting the small additional cost of manufacture arising from the utilization of the present apparatus. Additionally, a much higher quality window unit is achievedin both an aesthetic and functional sense. Thus, the presentinvention substantially eliminates the long standing problems arising from the occurrence of bowed sash members.

BRIEF DESCRIPTION OF THE DRAWINGS Referring tothe drawings wherein like numerals designate like elements of the invention throughout the various figures:

FIG. 1 is a diagramatic view ofa wooden rail member at various stages ofthe bow cutting and milling opera DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, the numeral 10 designates an elongated wooden rail having a generally rectangular transverse cross section. The rail 10 is shown at various stages of the bow cuttingand milling process provided by the present invention. While such a rail has numerous uses, the description herein will be directed to its application in the construction of wooden window sashes (i.e., as the head, check and side rail members comprising a conventional window sash). For such usage, it is desirable in both a functional and an aesthetic sense to have a minumum of bowing along the longitudinal axis of rail 10.

The elongated rail 10 has a pair of oppositely disposed, longitudinally extending surfaces 12 and 14 which, in accordance with the present invention, are milled in the following manner. In FIG. la, an unmilled rail 10 is shown in which the surfaces 12 and 14 are illustrated as being generally straight. A concave bow is first cut into the surface 12 as shown in FIG. lb. Next, rail is milled along surface 14 so as to define a U- shaped groove therein (not shown) for receiving a lite of glass. This is done with surface 12 of rail 10 held flush against a moulder guide (not shown) so as to remove the concave bow from surface 12 during the milling of surface 14. The milling of surface 14 creates forces within rail 10 which tend to cause the rail to bow in a direction so as to produce a concave bow along surface 14 as shown in FIG. 1c. However, when rail 10 is released from the moulder guide, the natural tendency of milled surface 14 to bow is counteracted by the concave bow milled in surface 12 resulting in a generally straight rail as shown in FIG. 1d. It should be understood that in many instances the unmilled rail 10 shown in FIG. 1a will have a natural bow along the longitudinal axis simply by virtue of the various stresses within the rail caused by the direction of the grain of the wood. As explained subsequently, rails 10 are automatically monitored to determine the direction of this natural bow, if any, and then positioned as shown in dotted lines in FIG. la (i.e., so that a concave bow is defined along the surface designated surface 12).

With reference to FIGS. 2 and 3, the apparatus provided by the present invention can be broadly described as comprising a hopper or magazine member 20, a wood cutting means 22, a conveyor means 24, and a discharge conveyor 26. The rail members 10 stored in hopper are continuously conveyed past cutting means 22 by conveyor means 24; the cutting means 22 cutting a concave bow along the surface 12 of each rail 10. The discharge conveyor 26 conveys the bowed rails to a subsequent stage of the milling operation (e.g., moulding apparatus for cutting a U-shaped groove in surface 14 as described above).

Specifically, hopper 20.is mounted on a horizontally extending platform 30 supported by a frame structure 31. As shown, the platform 30 defines a longitudinally extending slot 32 above which the rails 10 are positioned in a longitudinally extending overlapping relationship, the bottom rail being supported by the edges of slot 32. The hopper 20 includes a first upright 34a fixedly attached to platform 30. A second upright member 34b is attached to a plate 35 slideably carried by a track portion 300 of platform 30. Longitudinal movement of member 34b allows the distance between members 34a and 34b to be adjusted to accommodate wooden rails of varying lengths. A screw 36 having a knob 36a extends through plate 35 to engage track 300 and to securely fix member 3412 thereto. It should be readily apparent that various alternative means can be utilized to provide for the relative movement of the upright support members 34a and 34b. Finally, each of the upright members 34a and 34b includes a retaining member 37 which is laterally movable to adjust the distance between the members 37 and a longitudinally extending guide member 38 for receiving rails of different widths therebetween. A screw 39 having a knob 39a extends through a slot (not shown) in each of the upright members 34:! and 34b to engage the respective member 37 and to securely fix the member 37 thereto.

A curvature or how sensing means 40 is associated with hopper 20. Bow sensing mechanism 40 includes a base member 41 solidly mounted on track 30a carried by platform 30 for adjusting the position of mechanism 40 between upright members 34a and 34b of hopper 20. Typically, however, curvature sensing mechanism is positioned equi-distant the members 34a and 3412. A vertically extending member is attached to base 41 and has attached to the upper end portion thereof an arm member 46 pivoted about a pin 47. A roller 48 is attached to the lower end portion 46a of arm 46. As can be best seen in FIG. 5, the arm member 46 is spring biased so that the lower end portion 46a which extends angularly inward from upper arm portion 46b to engage the center of one of the rails 10 (e.g., in the illustrated embodiment, the rail fourth from the bottom). In its normal position, arm 46 is situated so that roller 48 engages the center of a straight rail 10 without causing any pivoting movement of the arm 46 (i.e., upper arm portion 46b is vertically extending). However, in the case where the rail 10 is bowed, the spring biased arm 46 will pivot either clockwise or counterclockwise from its normal position depending upon whether the curvature in the rail 10 is concave or convex, respectively.

An adjustable, actuating rod 50 is attached to upper arm portion 46b and engages a switching or signal producing mechanism 52 of thetype sold by Brunswick Engineering, Inc. of Northbrook, Illinois (e.g., a model 320 gauge probe used in combination with a Model BOO-R light box). The mechanism 52 produces a signal whenever pivot 46 moves a pre-determined distance in either a clockwise or counterclockwise direction resulting in a corresponding movement of actuating rod 50. For instance, in the case of acheck rail 34 inches in length, a bow exceeding one thirty-second of anvinch is typically considered unacceptable and, upon movement of roller 48 over such a distance, the mechanism 52 generates an electrical signal. This signal is transmitted to a pair of pneumatic cylinders 53a and 53b which are attached to the members 37 adjacent upright memv bers 34a and 34b, respectively. The prime mover 54 of each of the pneumatic cylinders 53a and 53b is directed toward the rails 10 and, upon the cylinder receiving a signal from curvature sensor 40, the cylinders are actuated causing the prime mover to eject the bowed rail from hopper 20. It should be understood that while the utilization of bow sensing mechanism 40 is highly desirable, its utilization is not essential to the operation of the present invention. 7

The wood cutting means 22 includes a blade member for cutting each rail 10, guide means 62 for guiding each rail past the blade member 60, and control means generally designated 64 for controlling the relative position of blade member 60 and guide means 62 so as to cut a concave curvature in each rail member 10 as the rail passes the blade 60. Specifically, the blade member 60 is attached to a spindle 65 mounted on a spindle block 66 and driven by motor 67 supported by frame 31. Spindle block 66 is reciprocally moveable in the direction normal to the direction of travel of rails 10. One such travelable, motorized spindle is sold by Gilman, Inc. as Model 4000 F-1-40-B1C. A hydraulic cylinder 68 which forms a part of such motorized spindles urges the spindle block 66 outward (i.e., away from the rails 10 as seen in FIG. 2). The reciprocal movement of spindle block 66 is provided by a drive cam 70 driven by motor 71 through a right angle gear converter 72. The converter 72 is connected to motor 71 via a chain 73 and a sprocket 74. Chain 73 is also connected to a sprocket 75 for the purposes subsequently described. A cam follower 76 is attached to a first end of an arm 77, a second end of arm 77 being pivotally attached to frame 31. A rod 78 is attached to spindle block 66 and engages arm 77 intermediate the two ends thereof so that, upon rotation of cam follower 76 and the resulting reciprocal movement of arm 77, the spindle block 66 is moved inwardly agains the bias of cylinder 68 and then outwardly upon the urging of cylinder 68 as arm 77 is moved outwardly by cam follower 76.

The guide means 62 includes the fixed guide rail 38 and a moveable guide 80 which is biased toward the cutter blade 60 so as .to urge the passing rail against the rail 38 and blade 60. As can be seen in FIG. 2, the guide 38 includes an opening 81 in which the blade 60 is positioned for the aforementioned lateral movement toward and away from the passing rails 10. Moveable guide member 80 includes two overlapping rail portions 84a and 84b pivotably attached to platform 30 and a pneumatic cylinder 85 having a prime mover 83 engaging guide rail 84a. The pneumatic cylinder 85 applies a constant pressure to the overlapping guides 84a and 84b urging the passing rail against fixed rail 38 and blade 60.

The conveyor means 24 includes a chain conveyor 88 which is driven by a drive wheel 89 attached to sprocket 75 and guided by a plurality of guide wheels 90, 91 and 92. The drive chain 88 is positioned so that a plurality of upright lugs 94 attached thereto project upwardly through the elongated slot 32 within platform 30. Upon rotation ofchain 88, the lugs 94 continuously engage the bottom one of the horizontally extending rails 10, discharging the bottom rail from hopper 20 and individually conveying the discharged rail past the blade 60.

As drive cam 70 and drive wheel 89 are connected via chain 73, the speed of endless chain 88 and the reciprocal movement of blade 60 are synchronized. That is to say, drive cam 70 makes one complete revolution per pusher lug. 94 on chain 88 (e.g., in the case of four pusher lugs 94 on chain 88, the cam 70 makes four revolutions per revolution of chain 88). As a result of this spacing of lugs 94 and the speed of chain 88, the drive cam 70 is caused to rotate one complete revolution for each passage ofa rail past the cutter blade 60. Thus, blade 60 moves inwardly toward rail 10 during the passage of the first half of the rail and then moves outwardly during the passage of the second half of the rail thereby cutting a concave bow within therail member lt should be understood, however, that this concave bow could be provided by other means. For example, blade 60 could be fixedly mounted and the guide member 80 adapted so as to provide a varying bias against each passing rail member 10 urging the surface 14 thereof against the blade 60 with varying degrees of force so that a concave curvature is cut in the surface 14. It should be further understood that the positioning of lugs 94 on chain 88 is dictated by the length of rails 10 and the amount of spacing desired between successive ones of the rails conveyed to the blade 60. For example, a rotational speed of 100 feet per minute for chain 88 has been found to be particularly desirable.

Finally, the discharge conveyor 26 conveys the rails 10 having a concave curvature cut therein by blade 60 to a subsequent stage in the milling operation (e.g., a machine for milling a U-shaped groove in surface 14 for receiving a window pane). Discharge conveyor 26 includes a pair of pneumatic cylinders 95 and 96 attached to frame 31. Each of the cylinders 95 and 96 includes a prime mover 98 for movement in a direction normal to the movement of rail 10. The operation of cylinders 95 and 96 is synchronized with the rotational speed of chain 88 (by means not shown) so that upon a rail 10 being conveyed by the chain 88 to a position extending between cylinders 95 and 96, the cylinders are actuated to eject the rail laterally onto a plurality of conveyor belts 99. The conveyor belts 99 convey the rail 10 to a subsequent stage of the milling process above described.

Since numerous modifications to the preferred embodiment described above will be readily apparent to the artisan, it is my intent to be limited solely by the spirit and scope of the appended claims.

What is claimed is:

1. A method for reducing the occurrence of bowing in wooden window sash rail members which are milled along one surface to form a groove for receiving a pane of glass, said method comprising the step of cutting a concave-curvature along a surface of the rail member opposite the surface milled so as to receive the glass pane, said curvature being sufficiently concave to overcome the natural tendency of the rail member to bow subsequent to the milling operation.

2. The method of claim 1 including the additional steps of:

a. storing a plurality of rail members in a horizontally I extending, vertically overlaying relationship;

b. continuouslyconveying the bottom one of the stored rail members past a cutter member for cutting said concave curvature; and

c. reciprocally moving said cutter member so that said member cuts said concave curvature in the passing rail member.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENTNO. 3,871,428

DATED I March 18, 1 INVENTOR) Kenneth L P terson It is certified that error appears in the ab0ve-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, Line 3 before opposite" insert --rail Column 5, Line 5 "agains"should be -against- Column 5, Line 17, prime mover "83" should be prime mover -86-- Signed and sealed this 3.51: day of July J75.

SEAL) RUTH C. I' IASON Commissioner of Patents Attesting Officer and Trademarks 

1. A method for reducing the occurrence of bowing in wooden window sash rail members which are milled along one surface to form a groove for receiving a pane of glass, said method comprising the step of cutting a concave curvature along a surface of the rail member opposite the surface milled so as to receive the glass pane, said curvature being sufficiently concave to overcome the natural tendency of the rail member to bow subsequent to the milling operation.
 2. The method of claim 1 including the additional steps of: a. storing a plurality of rail members in a horizontally extending, vertically overlaying relationship; b. continuously conveying the bottom one of the stored rail members past a cutter member for cutting said concave curvature; and c. reciprocally moving said cutter member so that said member cuts said concave curvature in the passing rail member. 